1. Field of the Invention
The present invention relates to a communication control system which conducts IP (Internet Protocol) packet distribution over an ATM (Asynchronous Transfer Mode) network and a communication control method thereof and, more particularly, to an ATM network communication control system attaining high-speed transmission through reduction of such packet transmission by hop-by-hop such as that by a router within a network, and a communication control method thereof.
2. Description of the Related Art
Among conventional art of this kind for conducting IP (Internet Protocol) packet distribution over an ATM network, the following four are well known.
Classical IP model and Tag Switching
MPOA
IP Switch
Cell Switch Router
Characteristics of the respective art will be described in the following.
a) Characteristics of Classical IP model and Tag Switching
FIG. 5 is a schematic diagram showing structure of an ATM network to which the classical IP model and a tag switching are applied. For communication between different IP sub-nets according to this art, a router is indispensable between the IP sub-nets as shown in FIG. 5.
Classical IP model and tag switching, however, have a drawback that no improvement can be expected of a transmission rate in communication between different IP sub-nets. The reason is that a router always intervening between IP sub-nets to conduct packet transmission by software processing bottlenecks packet transmission.
b) Characteristics of MPOA
FIG. 6 is a schematic diagram showing structure of an ATM network to which MPOA is applied. As illustrated in FIG. 6, an MPC (Multiprotocol Client) and an MPS (Multiprotocol Server) are provided in the network. This system employs LANE (LAN Emulation, LAN represents Local Area Network) and NHRP (Next Hop Resolution Protocol) techniques. Within the same IP subnet, an LANE protocol is used for communication. For communication between different IP sub-nets, an MPC first serves as a router and then a direct connection is set up between MPSs of a transmission source and a transmission destination to carry out communication.
In FIG. 6, for communication from an MPS1 to an MPS2, an MPC sets up a shortcut VC (Virtual Channel) to each of the MPS1 and the MPS2. At this state, the MPC serves as a router to carry out communication. If at this occasion, communication to the same destination is conducted frequently, an NHRP protocol operates, so that the MPC1 sets up a shortcut VC to the MPS2. At this state, direct communication is possible between the MPS1 and the MPS2 to enable high-speed transfer of packets.
MPOA, however, has a drawback that efficiency is not high because an end-to-end connection can be set up only after connections are established between adjacent MPC and MPS and between adjacent MPSs. The reason is that an end-to-end connection is enabled after the MPS sends or receives a protocol to/from its adjacent node.
Another drawback is that when a new packet is generated, load on an MPS in processing will be sharply increased. The reason is that when a new packet is generated, each node conducts address resolution and creation of a table by sending or receiving a protocol to/from its adjacent node.
A further drawback is that as a network is increased in scale, address resolution resources of the entire network are exponentially increased. The reason is that as the network is increased in scale, the number of entries in an address resolution table which the MPS has as well as the number of MPSs increases.
c) Characteristics of IP Switch
FIG. 7 is a schematic diagram showing structure of an ATM network to which an IP switch is applied. As illustrated in FIG. 7, an IP switch gateway (hereinafter abbreviated as GW) and an IP switch (hereinafter abbreviated as IPSW) are provided in the network. A GW mainly conducts termination of an IP switch network. An IPSW is mainly composed of a controller unit (hereinafter abbreviated as CTL) for forwarding an IP packet and a switch unit (hereinafter abbreviated as SW) for switching an ATM cell. A GW is connected to only one IPSW and belongs to a plurality of existing LANs. An IPSW is connected to a plurality of GWs and IPSWs. An IP sub-net provided between a certain IPSW and another IPSW has only these two nodes. Each port of the GW and the IPSW has an IP address.
As illustrated in FIG. 7, VCs are always being set up between adjacent devices. On this occasion, a CTL serves as a router to carry out communication by hop-by-hop. If communication to the same destination is conducted frequently, each node used in the communication sends an upstream node a request for preparing a dedicated VC. When there is no abnormality in particular, a dedicated VC will be set up between adjacent nodes. A specific protocol also causes a dedicated VC to be set up between adjacent nodes. When dedicated VCs are established both upstream and downstream the IPSW, the IPSW directly connects the VCs by an SW. In other words, the CTL is prevented from intervening in a communication path. Since at this state, no routing is conducted within the IPSW, packets can be transferred at a high speed.
Using an IP switch, however, has a drawback that efficiency is not high because an end-to-end connection can be set up only after dedicated VCs are established between adjacent GW and IPSW and between adjacent IPSWs. The reason is that an end-to-end connection is enabled after the IPSW sends or receives a protocol to/from its adjacent node.
Another drawback is a total lack of affinity with an approach of an ATM forum. The reason is that a unique protocol is adopted.
A further drawback is that an IP domain is wastefully consumed. The reason is that a port of an IPSW requires an IP address for terminating an IP protocol.
Still further drawback is that a routing protocol should be mounted on every ATM switch. In other words, an ATM network should be composed of IPSWs. The reason is that no communication is possible unless the IPSW conducts routing processing.
Still further drawback is that when a new packet is generated, load on an IPSW in processing will be sharply increased. The reason is that when a new packet is generated, each node conducts address resolution and creation of a table by sending or receiving a protocol to/from its adjacent node.
Still further drawback is that as a network is increased in scale, address resolution resources of the entire network are exponentially increased. The reason is that increase in scale of a network is followed by an increase in the number of entries in an address resolution table which the IPSW has as well as the number of the IPSWs.
d) Characteristics of Cell Switch Router
A cell switch router (hereinafter abbreviated as CSR) is provided in a network. A CSR is mainly composed of a CTL for forwarding an IP packet and an SW for switching an ATM cell. The CSR also conducts termination of a CSR network.
Basic operation of the cell switch router is similar to that of an IP switch. With a VC set up in advance between adjacent devices, the CTL carries out communication by hop-by-hop as a router does. For a specific packet, a dedicated VC is prepared between adjacent nodes which are to be connected by an SW. In other words, the CTL is prevented from intervening in a communication path. Since at this state, no routing is conducted within the CSR, packets can be transferred at a high speed. Protocol used is different from that used for an IP switch.
Conventional IP packet distribution techniques using the above-described cell switch router are recited, for example, in the literature xe2x80x9cCell Switch Routerxe2x80x94Basic Concept and Migration Scenarioxe2x80x9d (Yasuhiro Katsube, Ken-ichi Nagami, Shigeo Matsuzawa, THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, TECHNICAL REPORT OF IEICE. SSE95-201, IN95-145 (1996-03)) and the literature xe2x80x9cCell Switch Routerxe2x80x94Protocol Mechanism and Implementation Architecturexe2x80x9d (Shigeo Matsuzawa, Ken-ichi Nagami, Akiyoshi Mogi, Tatsuya Jinmei, Yasuhiro Katsube, THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, TECHNICAL REPORT OF IEICE, SSE95-202, IN95-146 (1996-03)).
Using a cell switch router, however, has a drawback that efficiency is not high because an end-to-end connection can be set up only after a dedicated VC is established between adjacent CSRs. The reason is that an end-to-end connection is enabled after the CSR sends or receives a protocol to/from its adjacent node.
Another drawback is a total lack of affinity with an approach of an ATM forum. The reason is that a unique protocol is adopted.
A further drawback is that an IP domain is wastefully consumed. The reason is that each port of a CSR requires an IP address for terminating an IP protocol.
Still further drawback is that a routing protocol should be mounted on every ATM switch. In other words, an ATM network should be composed of CSRS. The reason is that no communication is possible unless the CSR conducts routing processing.
Still further drawback is that when a new packet is generated, load on a CSR in processing will be sharply increased. The reason is that when a new packet is generated, each node conducts address resolution and creation of a table by sending or receiving a protocol to/from its adjacent node.
Still further drawback is that as a network is increased in scale, address resolution resources of the entire network are exponentially increased. The reason is that increase in scale of a network is followed by an increase in the number of entries in an address resolution table which the CSR has as well as the number of the CSRs.
An object of the present invention is to provide an ATM network communication control system capable of communicating without a router between different IP sub-nets and realizing speed-up of packet transmission and improvement in transmission efficiency and a communication control method thereof.
Another object of the present invention is to provide an ATM network communication control system which realizes speed-up of packet transmission and improvement in transmission efficiency by setting up an end-to-end connection with ease and at a high speed, and a communication control method thereof.
A further object of the present invention is to provide an ATM network communication control system which realizes improvement of transmission efficiency, saving of address resolution resources and effective use of an IP sub-net through simplification of structure of an ATM network, and a communication control method thereof.
Still further object of the present invention is to provide an ATM network communication control system having affinity with existing equipment improved by realizing acquisition of address information, notification of address information, setting of connections and other processing by an ATM-forum-based protocol, and a communication control method thereof.
According to the first aspect of the invention, a communication control system including a route server and an ATM switch provided on an ATM network, and edge switches for connecting the ATM network and other IP sub-networks to control a connection between an arbitrary one of the edge switches and the ATM switch, wherein
the route server comprises
information accumulation means for collecting and accumulating, from every the edge switches on the ATM network, an ATM address of the edge switch and information regarding the IP sub-network directly or indirectly reachable through the edge switch, and
information processing means for generating a table putting relationships between the IP sub-network reachable and an ATM address of a device to be passed through for reaching the IP sub-network together by using information accumulated in the information accumulation means and transmitting the table to all the ATM network,
the edge switch comprises
information notification means for notifying the route server of an ATM address of the device of its own and information regarding the IP sub-network directly or indirectly reachable through the device of its own,
address search means for searching network addresses of a destination of a packet for an ATM address of a device to be passed through with reference to a table sent from the route server, and
connection setting means for setting necessary connections including a switched virtual channel based on a search result obtained by the address search means.
In the preferred construction, various processing including acquisition of address information, notification of address information and setting of connections conducted by the route server and the edge switch are realized by an ATM-forum-based protocol.
In another preferred construction, the route server and the edge switch send and receive information as required any time after the device is started.
In another preferred construction, the route server exists only one on one the ATM network.
In another preferred construction, the route server and the edge switch send and receive information as required any time after the device is started, and
the route server exists only one on one the ATM network.
According to the second aspect of the invention, in a network system including a route server and an ATM switch provided on an ATM network, and edge switches for connecting the ATM network and other IP sub-networks, a communication control method of controlling a connection between an arbitrary one of the edge switches and the ATM switch, comprising the steps of:
at the route server,
collecting and accumulating, from every the edge switches on the ATM network, an ATM address of the edge switch and information regarding the IP sub-network directly or indirectly reachable through the edge switch, and
generating a table putting relationships between the IP sub-network reachable and an ATM address of a device to be passed through for reaching the IP sub-network together by using accumulated information, and
transmitting a generated table to all the ATM network, and
at the edge switch
notifying the route server of an ATM address of the device of its own and information regarding the IP sub-network directly or indirectly reachable through the device of its own,
searching network addresses of a destination of a packet for an ATM address of a device to be passed through with reference to a table sent from the route server, and
setting necessary connections including a switched virtual channel based on a search result.
In the preferred construction, various processing including acquisition of address information, notification of address information and setting of connections conducted by the route server and the edge switch are realized by an ATM-forum-based protocol.
In another preferred construction, the route server and the edge switch send and receive information as required any time after the device is started.
According to another aspect of the invention, in a network system including a route server and an ATM switch provided on an ATM network, and edge switches for connecting the ATM network and other IP sub-networks, a computer readable memory storing a control program for controlling a connection between an arbitrary one of the edge switches and the ATM switch, the control program comprising the steps of:
at the route server,
collecting and accumulating, from every the edge switches on the ATM network, an ATM address of the edge switch and information regarding the IP sub-network directly or indirectly reachable through the edge switch, and
generating a table putting relationships between the IP sub-network reachable and an ATM address of a device to be passed through for reaching the IP sub-network together by using accumulated information, and
transmitting a generated table to all the ATM network, and
at the edge switch
notifying the route server of an ATM address of the device of its own and information regarding the IP sub-network directly or indirectly reachable through the device of its own,
searching network addresses of a destination of a packet for an ATM address of a device to be passed through with reference to a table sent from the route server, and
setting necessary connections including a switched virtual channel based on a search result.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.